Backhoe needed to break up giant Minnehaha Creek ice jams

Ice chunks flow along in a rising Minnehaha Creek near 54th & Xerxes. Photo by Andrew Hazzard.

As a deep snowpack melts and new rain falls, the risk of flooding is rising along the Minnehaha Creek, putting city crews on constant lookout to break up ice jams at bottlenecks throughout the city.

“Days like today are really all hands on deck,” Rachael Crabb, the water resources supervisor at the Minneapolis Park & Recreation Board, said on March 14.

When the snow begins to melt, crews drive up and down the creek looking for bottlenecks and flooding.

“The biggest problem is ice jams,” Crabb said.

Ice jams form when thick ice chunks begin to break up in creeks and rivers, which can catch on logs and at bends in the water and dam up, which causes water to back up and spill over banks.

Minnehaha creek, which flows from Lake Minnetonka to the Mississippi River, largely falls under the management of the MPRB in its Minneapolis section. When Park Board crews spot ice jams, they call in help from the city’s Public Works department to get equipment capable of breaking up the jams and getting water flowing again.

There are a few common spots for ice jams along the creek in Minneapolis, Crabb said, including near Burroughs Elementary at 51st & James in Lynnhurst.

City crews had to use a backhoe to break up an ice jam there the morning of March 14, city media relations coordinator Sarah McKenzie said in an email. The crews also used the equipment at an ice jam point near 11th Ave. S. in the Hale neighborhood, she said.

Because Minnehaha Creek is so shallow, water is frozen down to the bed, Crabb said, meaning there’s not a lot of space for water to go as snow melts and rain falls.

In Minneapolis, the areas of most concern for flooding are between Lake Nokomis and Hiawatha Golf Course, where a series of low pedestrian bridges increase the risk of ice jams, according to Tiffany Schaufler, the Minnehaha Creek Watershed District’s project and land manager. Crabb said the area just upstream from Interstate 35W is also an area of flood concern.

“Anything low is going to be a problem,” Crabb said.

This year everything has lined up for a high flood potential in Minnesota. A wet fall, early heavy snow pack and a deep frost are indicators the National Weather Service looks for to identify flood potential, and the Twin Cities had all of them, Schaufler said.

To control flooding, the watershed district uses Gray’s Bay Dam at Lake Minnetonka to control flows before big rain events. The dam remains closed when the risk of ice jams is high.

The ideal situation to prevent flooding is to have warmer days and nights that dip below freezing, instead of everything melting right at once and overwhelming the creek bed, Schaufler said.

“Really what it comes down to is what the weather is going to do in the next couple of weeks,” Schaufler said.

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